262 research outputs found
Testing Yukawa-unified SUSY during year 1 of LHC: the role of multiple b-jets, dileptons and missing E_T
We examine the prospects for testing SO(10) Yukawa-unified supersymmetric
models during the first year of LHC running at \sqrt{s}= 7 TeV, assuming
integrated luminosity values of 0.1 to 1 fb^-1. We consider two cases: the
Higgs splitting (HS) and the D-term splitting (DR3) models. Each generically
predicts light gluinos and heavy squarks, with an inverted scalar mass
hierarchy. We hence expect large rates for gluino pair production followed by
decays to final states with large b-jet multiplicity. For 0.2 fb^-1 of
integrated luminosity, we find a 5 sigma discovery reach of m(gluino) ~ 400 GeV
even if missing transverse energy, E_T^miss, is not a viable cut variable, by
examining the multi-b-jet final state. A corroborating signal should stand out
in the opposite-sign (OS) dimuon channel in the case of the HS model; the DR3
model will require higher integrated luminosity to yield a signal in the OS
dimuon channel. This region may also be probed by the Tevatron with 5-10 fb^-1
of data, if a corresponding search in the multi-b+ E_T^miss channel is
performed. With higher integrated luminosities of ~1 fb^-1, using E_T^miss plus
a large multiplicity of b-jets, LHC should be able to discover Yukawa-unified
SUSY with m(gluino) up to about 630 GeV. Thus, the year 1 LHC reach for
Yukawa-unified SUSY should be enough to either claim a discovery of the gluino,
or to very nearly rule out this class of models, since higher values of
m(gluino) lead to rather poor Yukawa unification.Comment: 32 pages including 31 EPS figure
Phenomenological Implications of Deflected Mirage Mediation: Comparison with Mirage Mediation
We compare the collider phenomenology of mirage mediation and deflected
mirage mediation, which are two recently proposed "mixed" supersymmetry
breaking scenarios motivated from string compactifications. The scenarios
differ in that deflected mirage mediation includes contributions from gauge
mediation in addition to the contributions from gravity mediation and anomaly
mediation also present in mirage mediation. The threshold effects from gauge
mediation can drastically alter the low energy spectrum from that of pure
mirage mediation models, resulting in some cases in a squeezed gaugino spectrum
and a gluino that is much lighter than other colored superpartners. We provide
several benchmark deflected mirage mediation models and construct model lines
as a function of the gauge mediation contributions, and discuss their discovery
potential at the LHC.Comment: 29 pages, 9 figure
Bigger, Better, Faster, More at the LHC
Multijet plus missing energy searches provide universal coverage for theories
that have new colored particles that decay into a dark matter candidate and
jets. These signals appear at the LHC further out on the missing energy tail
than two-to-two scattering indicates. The simplicity of the searches at the LHC
contrasts sharply with the Tevatron where more elaborate searches are necessary
to separate signal from background. The searches presented in this article
effectively distinguish signal from background for any theory where the LSP is
a daughter or granddaughter of the pair-produced colored parent particle
without ever having to consider missing energies less than 400 GeV.Comment: 26 pages, 8 Figures. Minor textual changes, typos fixed and
references adde
R-parity violating resonant stop production at the Large Hadron Collider
We have investigated the resonant production of a stop at the Large Hadron
Collider, driven by baryon number violating interactions in supersymmetry. We
work in the framework of minimal supergravity models with the lightest
neutralino being the lightest supersymmetric particle which decays within the
detector. We look at various dilepton and trilepton final states, with or
without b-tags. A detailed background simulation is performed, and all possible
decay modes of the lighter stop are taken into account. We find that higher
stop masses are sometimes easier to probe, through the decay of the stop into
the third or fourth neutralino and their subsequent cascades. We also comment
on the detectability of such signals during the 7 TeV run, where, as expected,
only relatively light stops can be probed. Our conclusion is that the resonant
process may be probed, at both 10 and 14 TeV, with the R-parity violating
coupling {\lambda}"_{312} as low as 0.05, for a stop mass of about 1 TeV. The
possibility of distinguishing between resonant stop production and
pair-production is also discussed.Comment: 20 pages, 4 figures, 6 tables; Version accepted by JHE
TeV scale mirage mediation in NMSSM
We study the next-to-minimal supersymmetric standard model. We consider soft
supersymmetry breaking parameters, which are induced by the mirage mediation
mechanism of supersymmetry breaking. We concentrate on the mirage mediation,
where the so-called mirage scale is the TeV scale. In this scenario, we can
realize the up-type Higgs soft mass of O(200) GeV, while other masses such as
gaugino masses and stop masses are heavy such as 1 TeV or more. Cancellation
between the effective \mu-term and the down-type Higgs soft mass ameliorates
the fine-tuning in the electroweak symmetry breaking even for \mu=O(500) GeV.
The mixing between the doublet and singlet Higgs bosons is suppressed by
(\lambda/\kappa)/tan\beta. Then the lightest doublet Higgs mass naturally
reaches 125 GeV lifted by the new quartic coupling. The higgsino and singlino
are light and their linear combination is the lightest superparticle.Comment: 24 pages, 24 figures, Numerical analysis is replaced with the version
calculated by NMSSMTools. Comments and references are added on the suppressed
doublet-singlet mixing and cases in which the 125 GeV boson is the 2nd
lightest CP-even scalar. The version accepted by JHE
Many faces of low mass neutralino dark matter in the unconstrained MSSM, LHC data and new signals
If all strongly interacting sparticles (the squarks and the gluinos) in an
unconstrained minimal supersymmetric standard model (MSSM) are heavier than the
corresponding mass lower limits in the minimal supergravity (mSUGRA) model,
obtained by the current LHC experiments, then the existing data allow a variety
of electroweak (EW) sectors with light sparticles yielding dark matter (DM)
relic density allowed by the WMAP data. Some of the sparticles may lie just
above the existing lower bounds from LEP and lead to many novel DM producing
mechanisms not common in mSUGRA. This is illustrated by revisiting the above
squark-gluino mass limits obtained by the ATLAS Collaboration, with an
unconstrained EW sector with masses not correlated with the strong sector.
Using their selection criteria and the corresponding cross section limits, we
find at the generator level using Pythia, that the changes in the mass limits,
if any, are by at most 10-12% in most scenarios. In some cases, however, the
relaxation of the gluino mass limits are larger (). If a subset of
the strongly interacting sparticles in an unconstrained MSSM are within the
reach of the LHC, then signals sensitive to the EW sector may be obtained. This
is illustrated by simulating the \etslash, , and \etslash signals in i) the light stop scenario and ii) the light
stop-gluino scenario with various light EW sectors allowed by the WMAP data.
Some of the more general models may be realized with non-universal scalar and
gaugino masses.Comment: 27 pages, 1 figure, references added, minor changes in text, to
appear in JHE
Revealing the footprints of squark gluino production through Higgs search experiments at the Large Hadron Collider at 7 TeV and 14 TeV
The invariant mass distribution of the di-photons from the decay of the
lighter scalar Higgs boson(h) to be carefully measured by dedicated h search
experiments at the LHC may be distorted by the di-photons associated with the
squark-gluino events with much larger cross sections in Gauge Mediated
Supersymmetry Breaking (GMSB) models. This distortion if observed by the
experiments at the Large Hadron Collider at 7 TeV or 14 TeV, would disfavour
not only the standard model but various two Higgs doublet models with
comparable h - masses and couplings but without a sector consisting of new
heavy particles decaying into photons. The minimal GMSB (mGMSB) model
constrained by the mass bound on h from LEP and that on the lightest neutralino
from the Tevatron, produce negligible effects. But in the currently popular
general GMSB(GGMSB) models the tail of the above distribution may show
statistically significant excess of events even in the early stages of the LHC
experiments with integrated luminosity insufficient for the discovery of h. We
illustrate the above points by introducing several benchmark points in various
GMSB models - minimal as well as non-minimal. The same conclusion follows from
a detailed parameter scan in a simplified GGMSB model recently employed by the
CMS collaboration to interpret their searches in the di-photon + \etslash
channel. Other observables like the effective mass distribution of the
di-photon + X events may also reveal the presence of new heavy particles beyond
the Higgs sector. The contamination of the h mass peak and simple remedies are
also discussed.Comment: 23 pages, 7 figures, title and organization of the paper is changed,
detailed parameter scan in a simplified GGMSB model is added, conclusions and
old numerical results remain unchange
Twenty Years of SUGRA
A brief review is given of the developments of mSUGRA and its extensions
since the formulation of these models in 1982. Future directions and prospects
are also discussed.Comment: Invited talk at the International Conference BEYOND-2003, Schloss
Ringberg, Germany, June 10-14, 2003; 21 pages, Late
Constraints on supersymmetry with light third family from LHC data
We present a re-interpretation of the recent ATLAS limits on supersymmetry in
channels with jets (with and without b-tags) and missing energy, in the context
of light third family squarks, while the first two squark families are
inaccessible at the 7 TeV run of the Large Hadron Collider (LHC). In contrast
to interpretations in terms of the high-scale based constrained minimal
supersymmetric standard model (CMSSM), we primarily use the low-scale
parametrisation of the phenomenological MSSM (pMSSM), and translate the limits
in terms of physical masses of the third family squarks. Side by side, we also
investigate the limits in terms of high-scale scalar non-universality, both
with and without low-mass sleptons. Our conclusion is that the limits based on
0-lepton channels are not altered by the mass-scale of sleptons, and can be
considered more or less model-independent.Comment: 20 pages, 8 figures, 2 tables. Version published in JHE
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